Fog inhibitor for photographic emulsions



Patented Dec. 15, 1942 304,962 FOG INHIBITOR FOR PHOTOGRAPH) EMULB IONS Samuel E. Sheppard and Wlldemnr Vnnselow, Rochester, N. Y., aegis-non to Emma! Kodak Company. Rochester, N. 1., s corporation 0! New Jersey No Drawing. Application October 9, 1841, Serial No. 414,284

10 Claims.

This invention relates to fog inhibiting agents for photographic emulsions and to photographic emulsions containing them.

Photographic emulsions, particularly ultrasensitive emulsions are those containing color sensitizers exhibiting a tendency to tog. This fog manii'ests.itself as a uniform deposit of silver extending over ihe emulsion, It may be caused by exposing the emulsion in a room which is not completely dark or by development oi the him for protracted periods or at temperatures above normal. Highly sensitive emulsions are more likely to 05 than those of lower sensitivity owing to the small amount of energy required to make the silver halide grains developable.

It is, therefore, an obiect of the present inven tion to provide photographic emulsions oi enhanced stability and which do not exhibit a high tendency to fog. The compounds used for this purpose should not markedly lower the new sitivity of the light-sensitive materials in which they are incorporated. I

The use of amino-substituted derivatives of pyrimidine as fog inhibitors is described in Kendell U. 8. Patent 2,173,628, granted September 19, 1939, and in Davey a Knott U. 8. application Serial No. 847,489, filed July 25, 1940, now Pat'- ent No. 2,273,582 of February 17, 1942. These patents do not describe the use of amino-substi tuted thiopyrimidines as foe inhibitors.

We have new discovered that 2-mercapto-py-- lio'iiclines having an amino suhstituent in the 4 position or fl-positlon or both of the pyrimidine rim; are valuable to: inhibitors. The amino group may be a primary amino group or may be substituted with other uroups.

2-mercapto pyrimidine has the lollowlng struc-- turn] formula:

Amino derivatives of this compound which we have round suitable as antifogganta are as follows:

c-(Tn r1 wooiylumi-ii alonox'iollcmiimiooi -l' $1ilbti Prim-wot pyrimidine 4 N===U HNH:

u HB-ii JP-N NOBOrH I L-ii O H MmiMhydmxy-2-mercnpto-b tl'oullophenyluoi-pyrimidine Lamina-6h Mroty-b-(T-hydmxyi-mlfonaph mower-own o mmpto-pyrimidlna 16. Nu -CH as -o r .-n=n-- eom imi -NH, i smimrb(f-sulioplienylnoi'tmemptopyrlmidipo 5 In the preparation oi an emulsion containing the antidoggants used according to our invention, e solution 0! the tog inhibiting agent was made up in a suitable solvent such as water or 56 alcohol and this solution mixed with the emulelon. In the tests which we made, a high speed negative emulsion containing no sensitizing dyes or coating doctors and having a pH o! 1.1 was used. Stock solutions of the fog inhibiting oomlil pounds were made and these were added to the emulsion in varying amounts. The emulsions were coated on glass plates, dried and incubated to obtain a. substantial log on the control plate containing no fog inhibitor. Incubation was carried out at 48% C. for a period of time willcient to produce an appreciable amount of fog on the control plate. All of the plates were incubated for the same period of time.

The amount of fog inhibiting agent added to the emulsion is of importance since 11' too much of the fog inhibiting compound is added it may desensitise the emulsion. The exact amount that must be used varies without particular fog inhibiting compounds selected and with the type of emulsion used as regards Ira-in sine and alkalinity of the emulsion and ratio of the Ielatin to silver halide. However. we have found that with gelatino silver halide developing-out emulsions the amotmt of anti-foggant will generally vary between about .001 gram and 1 gram of antifoggant per 1000 cc. of emulsion. The fog inhibiting agents which we have found to be satisfactory may be used in various kinds of photographic emulsions. In addition to being useful in ordinary non-color-sensitized emulsions, they may also be used in ortho-chromatic or panchromatic emulsions or in X-ray emulalone. They can be used with or without sensitiming dyes and ii: used with sensitizing dyes may be added to the emulsion beiore or after such dyes.

The following table will serve in illustrate the amounts of the various specific fog inhibiting agents referred to above which we have found to be especially satisfactory. In each case the amount of fog inhibiting agent specified is used in 1000 cc. of gelatino silver halide emulsion containing from 5% to gelatin and the table indicates the solvent in which each of the agents was incorporated in the emulsion:

Elma um oeemullion Solvent Water. Water-+NsOH. Water+KOll Water+NaOTi Water. Water+NaOH Itlstobeunderstoodthatmoreorlessof the toe inhibiting agent than the amount indicated hithetahle above maybeused. Generally, howeves-,ifamuehgreauramountisusedinthe emulsion either no increased fog inhibiting effect is obtained or there is a marked decrease in sensitivity oi the emulsion.

It is to be understood that we consider as included within our invention all modifications and equivalents tailing within the scope of the appended claims.

We claim:

1. A photographic emulsion comprising a colloidal material having a sensitive silver salt dispersed therein and containing a Z-mercapto pyrimidine having an amino group in at least one of the positions in the pyrimidine ring. selected from the 4-position and the 6-position, in fog-inhibiting amount.

2. A photographic emulsion comprising a colloidal material having a sensitive silver salt dispersed therein and containing a Z-mercapto pyrimidine having a primary amino group in at least one of the positions in the pyrimidine ring. selected from the 4-position and the 6-position, in fog-inhibiting amount.

3. A photographic emulsion comprising a gel. atino-silver halide emulsion containing a 2-mercapto-6amino-pyrimidine in fog-inhibiting amount.

4. A photographic emulsion comprising a gelatino-silver halide emulsion containing a fi-mercaptoi -amino-pyrimidine in fog-inhibiting amount.

5. A photographic emulsion comprising a gelatino-silver halide emulsion containing a 2-mercapto-4,8-diami.no-pyrimidine in fog-inhibiflng amount.

6. A photographic emulsion comprising a gelatino-silver halide emulsion containing from about 0.001 gram to about 1 gram per liter oi emulsion of a il-mercapto-B-amino-pyrimidine.

'1. A photographic emulsion comprising a gelatino-silver halide emulsion containing from about 0.001 gram to about 1 gram per liter of emulsion of a Z-mercapto-t-amino-pyrimidine.

8. A photographic emulsion comprising a gelatino-silver halide emulsion containing from about 0.001 gram to about 1 gram per liter of emulsion of a 2-mercapto-4,8-amino-pyrimidine.

9. A gelatino-silver halide emulsion containing a tog-inhibiting amount 0! 4.8-diamino-8- mercaptopyrimidine.

10. A gelatino-siiver halide emulsion containing a fog-inhibiting amount of 4-amino-6-hydrory-il-mercaptopyrimidine.

SAMUEL E. SHEPPARD. WALDEMAR VANBELOW. 

